linux-kernel - [RFC PATCH 6/6] net: use kvmalloc with __GFP

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Date:   Thu, 12 Jan 2017 16:37:17 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Vlastimil Babka <vbabka@...e.cz>,
        David Rientjes <rientjes@...gle.com>,
        Mel Gorman <mgorman@...e.de>,
        Johannes Weiner <hannes@...xchg.org>,
        Al Viro <viro@...iv.linux.org.uk>, <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>,
        Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org
Subject: [RFC PATCH 6/6] net: use kvmalloc with __GFP_REPEAT rather than open coded variant

From: Michal Hocko <mhocko@...e.com>

fq_alloc_node, alloc_netdev_mqs and netif_alloc* open code kmalloc
with vmalloc fallback. Use the kvmalloc variant instead. Keep the
__GFP_REPEAT flag based on explanation from Eric:
"
At the time, tests on the hardware I had in my labs showed that
vmalloc() could deliver pages spread all over the memory and that was a
small penalty (once memory is fragmented enough, not at boot time)
"

The way how the code is constructed means, however, that we prefer to go
and hit the OOM killer before we fall back to the vmalloc for requests
smaller than 64kB in the current code. This is rather disruptive for
something that can be achived with the fallback. On the other hand
__GFP_REPEAT doesn't have any useful semantic for these requests. So the
effect of this patch is that requests smaller than 64kB will fallback to
vmalloc esier now.

Cc: Eric Dumazet <edumazet@...gle.com>
Cc: netdev@...r.kernel.org
Signed-off-by: Michal Hocko <mhocko@...e.com>
---
 net/core/dev.c     | 24 +++++++++---------------
 net/sched/sch_fq.c | 12 +-----------
 2 files changed, 10 insertions(+), 26 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 56818f7eab2b..5cf2762387aa 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -7111,12 +7111,10 @@ static int netif_alloc_rx_queues(struct net_device *dev)
 
 	BUG_ON(count < 1);
 
-	rx = kzalloc(sz, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
-	if (!rx) {
-		rx = vzalloc(sz);
-		if (!rx)
-			return -ENOMEM;
-	}
+	rx = kvzalloc(sz, GFP_KERNEL | __GFP_REPEAT);
+	if (!rx)
+		return -ENOMEM;
+
 	dev->_rx = rx;
 
 	for (i = 0; i < count; i++)
@@ -7153,12 +7151,10 @@ static int netif_alloc_netdev_queues(struct net_device *dev)
 	if (count < 1 || count > 0xffff)
 		return -EINVAL;
 
-	tx = kzalloc(sz, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
-	if (!tx) {
-		tx = vzalloc(sz);
-		if (!tx)
-			return -ENOMEM;
-	}
+	tx = kvzalloc(sz, GFP_KERNEL | __GFP_REPEAT);
+	if (!tx)
+		return -ENOMEM;
+
 	dev->_tx = tx;
 
 	netdev_for_each_tx_queue(dev, netdev_init_one_queue, NULL);
@@ -7691,9 +7687,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
 	/* ensure 32-byte alignment of whole construct */
 	alloc_size += NETDEV_ALIGN - 1;
 
-	p = kzalloc(alloc_size, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
-	if (!p)
-		p = vzalloc(alloc_size);
+	p = kvzalloc(alloc_size, GFP_KERNEL | __GFP_REPEAT);
 	if (!p)
 		return NULL;
 
diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c
index a4f738ac7728..594f77d89f6c 100644
--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c
@@ -624,16 +624,6 @@ static void fq_rehash(struct fq_sched_data *q,
 	q->stat_gc_flows += fcnt;
 }
 
-static void *fq_alloc_node(size_t sz, int node)
-{
-	void *ptr;
-
-	ptr = kmalloc_node(sz, GFP_KERNEL | __GFP_REPEAT | __GFP_NOWARN, node);
-	if (!ptr)
-		ptr = vmalloc_node(sz, node);
-	return ptr;
-}
-
 static void fq_free(void *addr)
 {
 	kvfree(addr);
@@ -650,7 +640,7 @@ static int fq_resize(struct Qdisc *sch, u32 log)
 		return 0;
 
 	/* If XPS was setup, we can allocate memory on right NUMA node */
-	array = fq_alloc_node(sizeof(struct rb_root) << log,
+	array = kvmalloc_node(sizeof(struct rb_root) << log, GFP_KERNEL | __GFP_REPEAT,
 			      netdev_queue_numa_node_read(sch->dev_queue));
 	if (!array)
 		return -ENOMEM;
-- 
2.11.0